The advent of transgenic animals has made possible study of the influence and regulation of various genes on the development of an organism. However, this technique has not generally been used to develop cell lines for use in tissue culture. Tissue culture of the lens epithelium has been a goal of lens researchers because it may afford an opportunity to develop in vitro systems to test the efficacy of anticataract agents, as well as to study some mechanisms of cataract formation. A recently obtained transgenic animal has the T-antigen from the SV40 virus linked to the alphaA-crystallin promoter. Cells from the lens of this animal that proliferate in the tissue culture environment have been shown to produce all the alpha-crystallins. These cells also synthesize the enzyme aldose reductase, which is induced under conditions of hyperosmolarity. The cell line has been used to study metabolic alterations that occur during incubation with naphthalene metabolites, compounds chosen because of naphthalene cataracts' similarity to subcapsular age-related cataracts in humans. The specific-activity of the enzyme DT-diaphorase was increased when cells were exposed to high levels of naphthalene metabolites. Extensive work with epithelial samples from human donor eyes has shown little difference between epithelium from various sites in the lens or between epithelium from young or old adult epithelium.